Method for inspecting core shroud using remote operated vehicle (ROV)

a technology of remote operation and core shroud, which is applied in the direction of instruments, nuclear elements, greenhouse gas reduction, etc., can solve the problems of increasing the risk of having scc issues in nuclear reactor components, grinding, machining, and high-temperature water adversely affecting the associated structure,

Active Publication Date: 2021-04-29
GE HITACHI NUCLEAR ENERGY AMERICAS
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The system provides a comprehensive and efficient inspection of core shrouds, capable of detecting cracks and monitoring their propagation across varying geometries, minimizing debris loss and breakdowns, and reducing radiation exposure for personnel.

Problems solved by technology

In many applications, such as nuclear reactors, steam driven turbines, or water deaerators, high-temperature water may adversely affect the associated structures by contributing to stress corrosion cracks, corrosion, erosion, and so forth.
For example, residual stresses often result from cold working, grinding, machining, and other thermo-mechanical metal treatments.
Thus, the operating environment for BWRs and PWRs may increase the risk of having SCC issues in nuclear reactor components.
However, for BWRs and PWRs, IASCC may be primarily due to neutron radiation.
The first and second overhanging ledges may complicate the design of systems for inspecting core shroud 200 and the development of methods for inspecting core shroud 200.
Although SCC, IGSCC, and IASCC have been studied, no “cure” has been found.
As a result, cracks continue to initiate and propagate in components of nuclear reactors.
Core shrouds may be particularly susceptible due to their extremely high neutron fluence as the nuclear reactor ages.
Structures near core shroud 110, such as jet pump assemblies 138 may make it difficult for currently available inspection devices to access certain weld locations on core shroud 110.
And because different nuclear reactors have different layouts, it may be difficult to design a single device capable of inspecting all of the core shrouds of a given operator of nuclear power plants.
Breakdowns of tooling can be costly in terms of increased time to inspect the nuclear reactor.
Typical ROVs used in underwater exploration generally may be too large for use in inspecting core shroud 110.
Thrust fans may be used to hold a smaller ROV against core shroud 110, but the thrust fans needed to produce the required thrust force may increase the size of the ROV, thereby limiting its accessibility.

Method used

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  • Method for inspecting core shroud using remote operated vehicle (ROV)
  • Method for inspecting core shroud using remote operated vehicle (ROV)
  • Method for inspecting core shroud using remote operated vehicle (ROV)

Examples

Experimental program
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first embodiment

[0201]Referring to FIG. 8A, one or more devices to create and / or maintain vacuum 880 may comprise impeller 824 operating in void 820 in order to create and / or maintain the low pressure or vacuum space in void 820 of body 850.

second embodiment

[0202]Referring to FIG. 8B, one or more devices to create and / or maintain vacuum 880 may comprise venturi valve 826 or jet, pump 828 or other pressurized water supply, and / or hose 830 configured to connect pump 828 to venturi valve 826. A control unit (not shown) may be configured to control pump 828. Pump 828 may draw water from the annulus and / or may supply the water to venturi valve 826. Pump 828 may be located, for example, at the top of core shroud 300, above a water level on the refueling floor. Pump 828 may be configured to recirculate water already in RPV 100.

[0203]One or more devices to create and / or maintain vacuum 880 relative to outer surface 316 of core shroud 300 may comprise, for example, a sealing system with a vacuum pad, an eductor or ejector with a pump (e.g., centrifugal), a venturi with a pump (e.g., centrifugal), a vacuum impeller, or a vortex attractor.

[0204]More generally, one or more devices to create and / or maintain vacuum 880 relative to outer surface 316...

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PUM

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Abstract

The method includes installing a system for inspecting the core shroud on the core shroud, driving the system horizontally around the core shroud, and using a sensor of the system to inspect the core shroud, where the system includes a trolley, an arm, a tether, and a remotely operated vehicle (ROV) for inspecting the core shroud. The ROV includes a body configured to be operatively connected to the tether, and the sensor is configured to be operatively connected to the body, and configured to provide inspection information of the core shroud. The arm is configured to be operatively connected to the trolley. The ROV is configured to be operatively connected to the arm via the tether, and the tether is configured to provide vertical position information for the ROV relative to the outer surface of the core shroud.

Description

CROSS REFERENCE TO RELATED APPLICATION[0001]This application is a divisional of U.S. application Ser. No. 15 / 237,979, filed on Aug. 16, 2016, the entire contents of which is hereby incorporated by reference.BACKGROUND1. Field[0002]Example embodiments generally relate to remotely operated vehicles (“ROVs”) for inspecting core shrouds of nuclear power plants. Example embodiments also relate to systems for inspecting core shrouds of nuclear power plants. Additionally, example embodiments relate to methods for inspecting core shrouds of nuclear power plants.2. Description of Related Art[0003]In many applications, such as nuclear reactors, steam driven turbines, or water deaerators, high-temperature water may adversely affect the associated structures by contributing to stress corrosion cracks, corrosion, erosion, and so forth. For example, high temperature waters may contribute to stress corrosion cracking (“SCC”) in materials, such as carbon steels, alloy steels, stainless steels, nick...

Claims

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Application Information

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Patent Type & AuthorityApplications(United States)
IPC IPC(8): G21C17/013G21C19/20G21C17/01G21C17/007
CPCG21C17/013G21C17/007G21C17/01G21C19/207Y02E30/30B25J11/00B25J5/007B25J9/0009B25J9/1674B25J19/02G21C17/00G01N29/265Y10S165/003F22B37/483F22B37/002
InventorVIGLIANO, VINCENT CARLMORRISON, WILLIAM AARONMERCIER, EDMUND S.
OwnerGE HITACHI NUCLEAR ENERGY AMERICAS